1. Field of the Invention
The invention relates to a fluidic system sensor for continuous and simultaneous detection of operating pressures and temperatures, more particularly a sensor housing containing temperature probe, a pressure sensor and bores and passages to the sensors in the sensor housing.
2. Description of the Related Art
Known measuring couplings for fluid systems consist of a coupling bushing under line pressure in the installed state for detection of working pressures and temperatures of fluid media. Spring-loaded and mechanically actuated check valves are located in the bores of these couplings.
This type of measuring coupling is used to provide testing or measuring connections on pressure lines. The coupling bushing is usually fixedly installed with screw threadings in the pressure line of a fluid system. A sealing nipple in the form of a hollow stud is screwed onto said coupling bushing fixedly connected to a hose by a union nut for the duration of the testing or measuring activities. The couplings may be connected under pressure, i.e., without shutting down the installation, by measuring lines to corresponding measuring instruments. Flexible measuring lines may be installed in a manner similar to electric cables, so that expensive laying of pipelines is avoided, for connection of fixedly installed instruments such as manometers, selective manometer switches, electric pressure transducers and manometric switches. The effective operating pressures in fluid lines may be measured directly by such measuring coupling without release of venting screws and screwed pipe connections. Couplings of this type are used in highly different structural elements and controls of fluid systems. A protective cap, equipped with external threading, is screwed onto the coupling bushing following disconnection of the coupling to prevent penetration of dirt into the bushing and for additional sealing in case the check valve is not tightly installed in the coupling bushing.
Temperatures of fluid media have been measured heretofore by temperature sensors fixedly installed in the fluid flow or installed in hermetically sealed immersion tubes.
In installations with immersion tubes, in numerous cases, the temperature of the housing or an intermediate value different from the medium temperature rather than the desired medium temperature is erroneously measured due to the lack of knowledge of the requirements of the measuring technique.
U.S. Pat. No. 4,096,754 describes a measuring coupling for fluidic systems for detection of operating pressures and temperatures, where the measuring probe extends through a mechanically actuable ball valve in the operating state. The valve must be closed immediately following the passage of the probe upon removal of the probe from the measuring coupling. Operating errors cannot be excluded due to forced setting of the position of the valve. The measuring coupling cannot be used in difficultly accessible locations because removal of the probe is cumbersome both mechanically and with respect to handling; considerable space is required in view of the rotating valve needed.
A further device for the measurement of high pressures and temperatures in a hydraulic or pneumatic system is shown in DE No. 26 30 640. The device is equipped with a piezo-resistive pressure gauge and an electric circuit and integrated in a housing into a single structural unit. A pressure gauge is located in an oil filled transmission membrane housing, with contact pins embedded in molded glass guides of the transmission membrane housing distributed over the circumference.
The pressure gauge unit is cemented onto a small base disk having a diameter larger than the unit. Passages distributed over the circumference are provided for thorough guidance of the contact pins, said passages corresponding to those of the transmission membrane housing. The contact pins lead from the electric contacts of the sensor out of the pressure gauge to the electronic means located outside the system which serves to supply the sensor system and amplify the signals generated. A compact measuring system connectable by a simple screw and measuring adapters to a pressurized hydraulic or pneumatic system cannot be constructed in this fashion.
To perform exact measurements in all areas it is necessary to provided adjusting devices, in particular for measurement of high pressures and pressures under extreme conditions such as, for example, at high temperatures. It is necessary to measure and evaluate the physical conditions prevailing in the immediate vicinity of the pressure sensor and affecting the measuring accuracy of the sensor in order to adjust the pressure sensor and to maintain the adjustment continuously through the measurements. Similar considerations are valid for temperature measurements.
DE-OS No. 30 00 110 describes a probe for temperature and pressure measurements, intended in particular for geothermic exploration applications. In this embodiment each probe has separate bores and passages through the sensor housing, so that measuring points are at different locations. The temperature sensors are located in the housing equipped with bores, therefore the fluids to be measured must flow through the bores into the housing. Such a probe is not suitable for accurate measurements of short term temperature fluctuations in fluid systems, as the probe significantly affects the system so that no genuine values are measured.
A further disadvantage of this layout is that in systems under pressure it is not feasible to connect the screw and measuring adapters to a bore to open the screw and measuring adapter as no connecting nipple is provided.